DOCSIS (Data Over Cable Service Interface Specification, data over cable service interface specification) is a communications standard that allows high-speed data transmission in an existing Cable TV network system. As shown in FIG. 1, a network to which a DOCSIS technology is applied mainly includes two types of devices: a CMTS (Cable Modem Termination Systems, cable modem terminal system) and a CM (Cable Modem, cable modem), where the CMTS is a large-scale device connected to a wide area network and may support more than ten thousands of subscribers, the CM is located on a remote subscriber side and is connected to a home network, and the CMTS and the CM are connected by using an HFC (Hybrid Fiber-Coaxial, hybrid fiber coaxial) network. The DOCSIS standard primarily supports implementation of IP data packet transmission between the CMTS and the CM.
During network data transmission, some real-time services (such as a voice service and a video service) have a relatively high requirement on quality of service (QoS, Quality of Service) of a network. On an existing DOCSIS network, DQoS (Dynamic Quality of Service, dynamic QoS) guarantee on the network is implemented by using some technical measures, for example, a PacketCable standard defined by CableLabs, where the PacketCable standard may implement dynamic QoS guarantee between a CMTS and a CM. An involved architecture and an involved interface, as shown in FIG. 2, include a UE (User equipment, user equipment), a CM, a CMTS, a PS (Policy Server, policy server), an AM (Application Manager, application manager), a P-CSCF (Proxy Call Session Control Function, proxy call session control function); in the PacketCable standard, different interfaces are used between the P-CSCF, the AM, the PS, the CMTS, the CM, and the UE. The following are specific descriptions of several types of involved interfaces:
ConnectedInterfacenetworknameelementsDescriptionpkt-mm-1CMTS-CMThe CMTS sends a DOCSIS-defined DSXmessage to the CM by using the pkt-mm-1interface, to control the CM to add,delete, or change a DOCSIS service flow(service flow) to dynamically implementa QoS request.pkt-mm-2PS-CMTSThe PS uses this interface to deliver aQoS policy to the CMTS; the CMTS uses thisinterface to report a QoS policyprocessing result.pkt-mm-3AM-PSThe AM uses this interface to instructthe PS to deliver a QoS policy to theCMTS; the PS uses this interface tonotify the AM of a result of processing,by the CMTS, the QoS policy.GmUE-P-CSCFThe UE and the P-CSCF implementregistration and session control byusing this interface.RxP-CSCF-AMThe P-CSCF and the AM implement sessionpolicy control and QoS resourceinformation exchange by using thisinterface.pkt-qos-2 PS-CMTSThe PS uses this interface to determinea CMTS connected to the UE device, wherethe interface uses the CPD (Control PointDiscovery) protocol.
In an existing DOCSIS network architecture, establishing a session that requires resource reservation generally includes the following procedure:
Step S1: An AM receives a request, sent by a P-CSCF, for performing resource reservation for a to-be-established session.
When a subscriber end initiates a request for a session that requires resource reservation, a call server of the session instructs, by using the P-CSCF, the AM to perform resource reservation for the foregoing session.
Step S2: The AM transmits a Gate-Set resource reservation request message to a PS, where the Gate-Set resource reservation request message includes a QoS parameter and a packet flow classification parameter.
Step S3: After receiving the Gate-Set resource reservation request message, the PS converts the Gate-Set resource reservation request message, and then forwards a Gate-Set resource reservation request message obtained by the conversion to a CMTS.
Step S4: The CMTS sends a dynamic service addition request DSA-REQ to a CM after receiving the Gate-Set resource reservation request message.
Step S5: The CM receives the foregoing service addition request DSA-REQ, adds a service flow (service flow) to respond to the service addition request, and replies to the CMTS with a dynamic service addition response DSA-RSP.
Step S6: The CMTS replies to the CM with a dynamic service addition acknowledgement DSA-ACK.
Step S7: The CMTS sends a Gate-Set-ACK resource reservation acknowledgement message to the PS.
Step S8: The PS sends the resource reservation response message to the AM.
Step S9: The AM receives a resource activation request that is sent by a session server by using application layer signaling.
After local resource reservation of the subscriber end is complete, a session server at an application layer initiates a connection request to a peer end of the session; after the peer end receives a session request, the session server instructs, by using the P-CSCF, the AM to activate a resource reserved for the session.
Step S10: The AM transmits a Gate-Set resource activation request message to the PS, where the Gate-Set resource activation request message includes a QoS parameter and a packet flow classification parameter.
Step S11: After receiving the Gate-Set resource activation request message, the PS converts the Gate-Set resource activation request message, and then forwards a Gate-Set resource activation request message obtained by the conversion to the CMTS.
Step S12: The CMTS sends a dynamic service change request DSC-REQ to the CM after receiving the Gate-Set resource activation request message.
Step S13: The CM receives the foregoing dynamic service change request DSC-REQ, changes an attribute of a service flow to an activated state, and replies to the CMTS with a dynamic service change response DSC-RSP.
Step S14: The CMTS replies to the CM with a dynamic service change acknowledgement DSC-ACK.
Step S15: The CMTS sends a Gate-Set-ACK resource activation response message to the PS.
Step S16: The PS sends the resource activation response message to the AM.
So far, QoS resource reservation and activation that are required during a session of a subscriber end are implemented, and the subscriber end can start a session interaction process.
With increasing requirements of subscribers on data services, to increase data bandwidth of a subscriber, a DOCSIS-based C-DOCSIS (China DOCSIS) technology emerges. As shown in FIG. 3, compared with a conventional network architecture in a DOCSIS technology, in a network architecture in the C-DOCSIS technology, a CMTS is moved down from a Hub equipment room to an optical node, and a quantity of subscribers served by the CMTS is reduced. A CMTS in this form is also referred to as a CMC (Cable Media Converter, cable media converter). An advantage of this type of network architecture lies in that, after the CMTS is moved down, supported subscribers are reduced, and larger bandwidth may be provided for each subscriber. After the CMTS is moved down to the optical node, a quantity of CMTSs is greatly increased, and a convergence device needs to be added to a network to converge the CMTSs located on optical nodes, where the convergence device may be a device such as an OLT (optical line terminal, optical line terminal), a switch, or a router. Generally, one convergence device may be connected to tens of or more CMTSs.
When an original dynamic QoS mechanism defined in PacketCable is applied to a C-DOCSIS network, some problems may occur:
On an original DOCSIS network, one CMTS may support at most tens of thousands of subscribers, and in this case, only hundreds of or less CMTS devices are required for serving ten million subscribers. However, on a C-DOCSIS network, because a CMTS device is moved down and one CMTS device generally supports only hundreds of or less subscribers, a large quantity of CMTS/CMC devices are required on the C-DOCSIS network, but a device implementing a Policy Server function generally supports only a relatively small quantity of CMTS devices (for example, 256 CMTS devices) for consideration of implementation complexity, capacity, and the like, and the large quantity of CMTS/CMC devices on the C-DOCSIS network can hardly be supported. Therefore, a resource reservation method applicable to the original DOCSIS network cannot be properly applied to the C-DOCSIS network.